Genetic improvement of kraft pulp yield in Eucalyptus nitens using cellulose content determined by near infrared spectroscopy

Abstract

Eucalyptus nitens (Deane & Maiden) Maiden (shining gum) is widely grown for kraft pulp production in many cool temperate regions of the world. Improving the kraft pulp yield of this species is important for increasing plantation profitability, but traditional assessment is slow and expensive. Cellulose content, which is strongly correlated with pulp yield, has been used as an alternative in tree breeding programs. However, a direct measure of cellulose content still relies on wet chemistry, limiting the number of samples that can be processed and the subsequent gains that can be made in a tree breeding program. An indirect method such as near infrared (NIR) spectroscopy provides a large increase in the numbers of samples that can be analysed. In this study, the genetic gains in cellulose content of E. nitens were compared using cellulose content, determined using wet chemistry and predicted by NIR calibrations based on different sampling intensities. Genetic gains based on NIR-predicted cellulose content were high, and a large proportion of the gain was achievable using a direct measure of cellulose. Calibrations were robust and generally could be reliably used across sites. NIR-predicted cellulose is highly heritable, with heritabilities comparable to or better than direct measures of cellulose.

La teneur en cellulose comme un trait de sélection pour l’amélioration du rendement en pâte kraft d’Eucalyptus urophylla

“…The reasonably good correlations between pulp yield and cellulose content either from disks or increment cores indicated that cellulose content determined by the diglyme-HCl method is a good predictor of pulp yield as previously has been shown in E. globulus and E. nitens (Wallis et al, 1997;Raymond and Schimleck, 2002;Schimleck et al, 2004). Cellulose content determined by this method had high repeatability (r = 0.96−0.98) with small standard deviation of duplicate measurements (about 1% of the mean) indicating that cellulose content measured by this method can give reliable results.…”

“…The somewhat higher standard deviation obtained for the estimate of pulp yield duplicates (0.68%, or about 1.4% of the mean) contributes to imprecision of the relationships between cellulose and pulp yield. Several recent studies evaluating cellulose content have used NIR (near infrared reflectance) prediction of cellulose, using calibrations developed from a sub-set of the samples that have been chemically analysed for cellulose (Raymond and Schimleck, 2002;Schimleck et al, 2004;Apiolaza et al, 2005). Such calibrations enable accurate prediction of cellulose content from NIR information in E. globulus and E. nitens (R 2 = 0.83−0.92) (Raymond and Schimleck, 2002;Schimleck et al, 2004).…”

“…Several recent studies evaluating cellulose content have used NIR (near infrared reflectance) prediction of cellulose, using calibrations developed from a sub-set of the samples that have been chemically analysed for cellulose (Raymond and Schimleck, 2002;Schimleck et al, 2004;Apiolaza et al, 2005). Such calibrations enable accurate prediction of cellulose content from NIR information in E. globulus and E. nitens (R 2 = 0.83−0.92) (Raymond and Schimleck, 2002;Schimleck et al, 2004). NIR prediction is faster than the direct measure using diglyme-HCl method (Schimleck et al, 2004) and its use would increase the number of samples that can be analysed.…”

“…These focus mainly on two temperate eucalypt species, E. globulus and E. nitens (Apiolaza et al, 2005;Kube et al, 2001;Raymond and Schimleck, 2002;Schimleck et al, 2004), and Populus deltoides (Olson et al, 1985). Narrow-sense heritability of cellulose content is reported to be high, ranging from 0.32 to 1 (Apiolaza et al, 2005;Kube et al, 2001;Raymond and Schimleck, 2002;Schimleck et al, 2004), but the coefficient of additive genetic variation in one study was low (3%) (Apiolaza et al, 2005). Genetic gain in cellulose content from selecting the top 5% of the population, in studies by Kube et al (2001) and Schimleck et al (2004), was about 3-4% of the original population mean, with little effect on growth or wood density.…”

“…Narrow-sense heritability of cellulose content is reported to be high, ranging from 0.32 to 1 (Apiolaza et al, 2005;Kube et al, 2001;Raymond and Schimleck, 2002;Schimleck et al, 2004), but the coefficient of additive genetic variation in one study was low (3%) (Apiolaza et al, 2005). Genetic gain in cellulose content from selecting the top 5% of the population, in studies by Kube et al (2001) and Schimleck et al (2004), was about 3-4% of the original population mean, with little effect on growth or wood density. Such levels of genetic improvement could reduce total pulping cost by 2-3% (Greaves and Borallho, 1996).…”